\ifx \allfiles \undefined
\documentclass{book}
\usepackage{rails-handbook-cn}
\begin{document}
\fi
%==============================
\chapter{模型 Models}
\section{迁移 Migration}
\label{sec:migration}\index{migration}

\section{find}
\label{sec:find}\index{find}

\section{虚拟属性 Properties}
\label{sec:virtual_property}\index{virtual_property}

\section{验证 Validates}
\label{sec:validate}\index{validate}


%==============================
\ifx \allfiles \undefined
\end{document}
\fi